clang-generated code with infinite loop segfaults

[charles-cooper]

the following code segfaults on any optimization level besides -O0:

#include "stdio.h"

int main() {
    printf("enter1\n");
    unsigned int i, sum = 0;
    for (i = 10; i >= 0; --i) {
        sum += i;
    }
    printf("sum = %u\n", sum);
}

repro:

~ $ clang --version
Ubuntu clang version 14.0.0-1ubuntu1.1
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
~ $ clang -O1 bug.c -o bug && ./bug
enter1
Segmentation fault (core dumped)

probably related: #60622

[charles-cooper]

note that with the first print statement removed, the program simply terminates without doing anything.

#include "stdio.h"

int main() {
    unsigned int i, sum = 0;
    for (i = 10; i >= 0; --i) {
        sum += i;
    }
    printf("sum = %u\n", sum);
}

[EugeneZelenko]

Could you please try 19 or main branch? https://godbolt.org should be helpful.

Only most recent release is maintained.

[charles-cooper]

same behavior. i've included IR output to help

https://godbolt.org/z/1WjPKrf7h

[dtcxzyw]

Non-trivial infinite loops are UB: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p2809r3.html
If you want the infinite loop behaves as is (i.e., get stuck without segfaults), please use the trivial form: https://godbolt.org/z/K8rxrEPrM